A new broadband circularly polarized (CP) square slot antenna is evaluated numerically and verified experimentally. The proposed antenna uses a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). Two symmetrical F-shaped slits embedded in opposite corners of ground plane are designed to obtain an excellent CP bandwidth. By adjusting the dimensions of the lightening-shaped feedline, the CP bandwidth can be further enhanced. Measured results show that the 3-dB axial-ratio bandwidth of the proposed antenna can reach 51.7% (2150 MHz-3650 MHz), and the impedance bandwidth is as large as 60.2% (2150 MHz--4000 MHz) with VSWR ≤ 2. Measured results are in good agreement with the simulation. The proposed antenna can be easily fabricated because of the simple coplanar geometry.

A fully fabric triangular shaped microstrip patch antenna is proposed for Wireless Broadband (WiBro) communication systems operating in the frequency range of 2.3 GHz to 2.4 GHz with 2.34 GHz as centre frequency. Three highly efficient and flexible antennas, built using three different conductive fabrics and an insulating polyester fabric are evaluated and results reported in this paper. To the best of authors' knowledge, this is the first attempt to utilize textile materials for the development of WiBro antennas.

A helix slow-wave structure (SWS) for a high efficiency Ku-band 140 W space TWT has been designed. Cold circuit parameters of helix SWS like propagation constant and on axis interaction impedance were determined using 3-D electromagnetic field simulators ANSOFT-HFSS and CST-MWS and validated with the experimental results. In-house developed large-signal code SUNRAY-1D was used to design the complete helix SWS in 2-section with sever and taper to achieve desired output power, gain, efficiency, and other linearity parameters such as phase shift, AM/PM factor, I/M components. Simulated RF performance of the Ku-band 140W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found.

Excitation of electromagnetic ion-cyclotron instability in the magneto plasma in the presence of perpendicular A.C. electric field for a generalized distribution function for background cold electrons and hot ion plasma has been studied. This distribution function is reducible to anisotropic and loss-cone type for different values of spectral index j. The particle trajectories have been estimated and used to find the dispersion relation and growth rate by using the method of characteristic solutions. Temporal electromagnetic ion cyclotron instability for various plasma parameters has been studied. The role of choice of parameters, distribution function and simultaneous presence of a.c. electric field is studied for excitation of electromagnetic ion cyclotron instability. The results have been used to explain the satellite observations of AMPTE/CCE and compared with earlier work done for temperature anisotropy and other types of distribution functions using other techniques.

The reliability of circuits on printed circuit boards (PCBs) in many modern electronic products is affected by severe noise caused by high-speed and low-voltage operation as well as layout constraints compounded by limited space and high circuit density. Crosstalk is a major noise source that interferes with the signal integrity (SI) in poor PCB layout designs. One common method of reducing crosstalk is the three-width (3-W) rule. The serpentine guard trace (SGT) approach has also been used to reduce crosstalk using two terminal matching resistors on the SGT between the aggressor and victim. Although the SGT approach suppresses far-end crosstalk (FEXT) at the expense of more layout space, it also neglects interference caused by near-end crosstalk (NEXT). In this study, we propose the SGT via (SGTV) approach in which grounded vias are added to the SGT at appropriate locations, and the ratio between the lengths of the horizontal and vertical sections of the guard trace is adjusted to minimize NEXT and FEXT. Frequency domain simulated (measured) results showed that the SGTV approach reduced NEXT by 3.7 (7.65) and 0.83 (1.6) dB as well as FEXT by 5.11 (7.22) and 0.1 (1.98) dB compared to the 3-W and SGT approaches, respectively. In the time domain, simulated (measured) results showed that SGTV reduced NEXT by 34.67% (49.8%) and 27.5% (26.65%) as well as FEXT by 46.78% (56.52%) and 6.91% (24.8%) compared to the 3-W and SGT approaches, respectively. Our proposed approach thus effectively suppresses both NEXT and FEXT to achieve better SI in PCB layout designs than the other two methods. As our design uses two grounded vias instead of two guard trace terminators and does not require extra components, it is less costly than SGT. Our simulated and measured results indicate that our approach is suitable for practical application because of the lower cost and the ease of implementation that eliminates NEXT and FEXT.

Scattering of electromagnetic radiation by a charged homogeneous spherical particle/body is treated. Theoretical solution represents a generalization of the Mie's scattering theory for electrically neutral sphere. It is shown that classical and quantum physics approaches may lead to different conclusions, as documented by numerical computations assuming various permeabilities, refractive indices, surface charges, temperatures, and other physical parameters of the spherical particles. Two discrete wavelengths (5 μm and 1mm) of the incident radiation are considered. Optical properties of charged particles composed of absorbing and slightly absorbing materials can essentially differ. Especially, the resonance peaks typically occur when imaginary part of particle refractive index is low. The relative permeability of a material may differ from unity at large wavelengths, e.g., in microwave region. Basically, the relative permeability appears to be less important factor than the surface charge. However, the permeability can influence the scattering and extinction efficiencies, as well as the backscattering features of small particles, under some conditions.

A compact multiband (GSM/DCS/PCS/UMTS/Bluetooth/WLANs/ Wi-MAX) planar monopole antenna, which contains multiple branches, is proposed in this work. Most wireless communication bands for consumer electronics are covered in this design. The antenna radiator comprises four resonant branches on the top surface of a PCB board and one parasitic element on its back. The antenna size is 17.5 mm×35.7 mm, and no via is needed in the fabrication process. Various techniques, such as branching, meandered lines, closed loop, capacitive coupling, parasitic elements and tapered ends, are used to enhance the antenna's bandwidth, matching and size reduction performance. Simulation and measurement show good agreement for reflection coefficient. The proposed antenna is particularly attractive for mobile devices that integrate multiple systems.

Two extended doublet bandpass filters with compact size and good spurious suppression characteristic are proposed. One is built up by a dual-mode microstrip resonator with a full-mode substrate integrated cavity, while the other is composed of a microstrip resonator and a half-mode cavity. The relationship between the location of their transmission zeros and the impedance ratio of the microstrip resonator is analyzed theoretically. Our proposed filters only occupy the areas of 0.69λ₀²/ε_r and 0.51λ₀²/ε_r, and they also have wide upper stopband. The predicted performances are demonstrated by the reasonable agreement obtained between their simulated and measured S-parameters.

Scattering of electromagnetic plane waves from an infinitely long nihility cylinder, coated with a chiral layer of uniform thickness, is presented. Cylindrical vector wave functions have been used to express the fields in different regions. The solution is determined by solving the wave equation for different regions and applying the appropriate boundary conditions at the discontinuities. Both TM and TE polarizations as incident plane wave have been considered in the analysis. Obtained Numerical results for the chiral-coated nihility cylinder are compared with a chiral-coated PEC cylinder.

A novel adaptive Wireless-Fidelity (Wi-Fi) system is the combination of radio frequency identification (RFID) technology, programmable intelligent microcontroller development board (PIDB) and reconfigurable antenna with beam shape characteristics. The system is capable to sustain a Wi-Fi signal adaptively above its threshold level (-81 dBm) within a range up to 100 m across three different buildings with variety indoor environments and floors. It is found that the modified ground reflection model has successfully predicted the total path loss of the test-bay buildings which consist of corridors, several floors and windows. The modified propagation model is extremely crucial in determining the projection and height of reconfigurable antenna to efficiently cover the scattered measurement points across the three buildings. The need of comparable signal strength is compulsory since the signal strength between 2.4 GHz of reconfigurable beam shape antenna and 0.433 GHz of RFID tag is different within the same distance. When reconfigurable beam shape antenna radiates with a minimum gain of 4.85 dBi, the measured signal strength shows that most of the measurement points are below Wi-Fi‟s threshold level which is from -69.001 dBm to -115.4530 dBm. However, the proposed system is able to boost all the signal strength above the threshold level with three different gain of reconfigurable beam shape antenna, 7.2 dBi, 9.9 dBi and 14.64 dBi through the activation of mobile RFID tag at different measurement points at one time. The boosted signal strengths are within the range of -69 dBm to -73.056 dBm. The capability of the mobile RFID tag in producing certain level of signal strength has been successfully exploited as a wireless stimulator for the system to adaptively activate certain PIN diode switches of reconfigurable beam shape antenna in this finding. The proposed system also has a great potential in realizing a new smart antenna system replacing the conventional switching beam array (SBA) antenna.

In this paper, based on different influences of the lattice symmetry, the geometry of dielectric rod, and the structure of unit cell to absolute gaps we propose a so-called three-order-effect method for the construction of two-dimensional (2D) photonic crystals (PCs) with larger absolute gaps. As an example, by means of our approach we fabricate a 2D hexagonal lattice of cylinder with an optimal rod adding at the center of the unit cell, where the absolute gap is larger than that of the PC with similar structure studied by other group previously. On the other hand, we also find that many of the 2D PCs with larger absolute gaps reported previously possess optimal first-order and second-order substructures. Our three-order-effect method would be useful for the design of 2D PCs with larger absolute gaps.

This paper presents an improved approach for the propagation of electromagnetic (EM) fields along a helical hollow waveguide that consists of two bendings in the same direction. In this case, the objective is to develop a mode model for infrared (IR) wave propagation, in order to represent the effect of the radius of the cylinder of the helix and the step's angle on the output fields and the output power transmission. This model enables us to understand more precisely the influence of the step's angle and the radius of the cylinder of the helix on the output results of each section (bending). The output transverse components of the field, the output power transmission and the output power density for all bending are improved by increasing the step's angle or the radius of the cylinder of the helix, especially in the cases of space curved waveguides. This mode model can be a useful tool to improve the output results in all the cases of the helical hollow waveguides with two bendings for industrial and medical regimes.

Simultaneous switching noise (SSN) is a significant problem in high-speed circuits. To minimize its effect and improve the electrical characteristics of circuits such as signal integrity (SI) and power integrity (PI), a novel power plane with planar electromagnetic bandgap (EBG) structure is proposed for SSN suppression in printed circuit boards (PCB) in this paper. In which a kind of improved long bridge is used and the equivalent parallel inductance can be increased significantly. Compared to the typical spiral bridge EBG structure with the same parameters, the long bridge EBG structure will change bandgap into dual-band, with lower center frequency and wider bandwith. The effectiveness and accuracy of this structure are verified by both simulations and measurements.

Early detection of tumor tissue is one of the most significant factors in the successful treatment of breast cancer. Microwave Breast Imaging methods are based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. When the breast is illuminated with a microwave pulse, the dielectric contrast between these tissues can result in reflected backscatter. These reflected signals, containing tumor backscatter, are spatially focused using a beamformer which compensates for attenuation and phase effects as the signal propagates through the breast. The beamformer generates an energy profile of the breast where high energy regions suggest the presence of breast cancer. Data-Adaptive (DA) beamformers, use an approximation of the desired channel response based on the recorded signal data, as opposed to Data-Independent (DI) algorithms which use an assumed channel model. A novel extension of the DA Robust Capon Beamformer (RCB) is presented in this paper which is shown to significantly outperform existing beamformers, particularly in a dielectrically heterogeneous breast. The algorithm is evaluated on three anatomically accurate electromagnetic (EM) breast models with varying amounts of heterogeneity. The novel beamforming algorithm is compared, using a range of performance metrics, against a number of existing beamformers.

Central Force Optimization (CFO) is a new multi-dimensional search metaheuristic based on the metaphor of gravitational kinematics. In this paper, for the first time, the CFO is applied to the optimal design of multilayer microwave absorbers (for normal incidence) in a specific frequency range. Several numerical examples are presented, in which the CFO results are compared with those found by other evolutionary algorithms. It is shown that the CFO results are comparable to those found by the self-adaptive differential evolution (SADE) algorithm and better than those found by particle swarm optimization (PSO) and gravitational search algorithm (GSA).

The memristor theory of Chua [1] provides a connection with the charge and magnetic flux in an electric circuit. We define a similar relation for the electric and magnetic flux densities in electromagnetism. Such an attempt puts forward interesting results. For example, the magnetic charges do not exist in nature however the electric charges behave as the magnetic monopoles in special media. We support our theory with results of the recent experiments on materials named as spin ice.

This paper proposes a novel design criterion for optimal pyramidal horns. According to it, the optimal aperture phase error parameters of a pyramidal horn are determined from the minimization of the horn's lateral surface area. We present two families of curves that illustrate the optimal aperture phase error parameters for frequency and directivity values in the area of practical interest. We also discuss two simple approximate design methods for the calculation of the optimal horn parameters. Comparisons with well-known design methods demonstrate the efficacy of our approach. The proposed criterion produces the lightest horn for a given directivity; as a result its fabrication requires less material compared to other structures. Moreover, the designed horns have smaller aperture area and occupy less space. The present approach is a useful design tool when the size and weight of a pyramidal horn or its manufacturing cost are of concern.

The results of an ultrawideband (UWB) measurement campaign carried out in a Hercules C-130 military cargo airplane are presented. The environment encompasses several metallic surfaces resulting in a large number of multipath components. Path-loss factor n representing the distance dependence of the channel path-loss is calculated for various frequency centers and bandwidths. A path-gain calculation model based on the concept of seperability of distance and frequency variables is proposed and comparison to measurements is given. Furthermore, time dispersion parameters, namely mean excess delay and root mean square (r.m.s.) delay spread are examined and their dependence on transmitter-receiver antennas separation is investigated. A power law is then employed to model the relation between the number of multipath components and the r.m.s delay spread. The temporal correlation between adjacent path amplitudes is found to be negligible. A modified Saleh-Valenzuela model is invoked to describe the clustering of multipaths, where a different power decay factor is used for the rays of the first cluster as opposed to subsequent clusters. Moreover, the Weibull distribution models the small scale channel fading with a lognormally distributed shape parameter. The average values of this parameter imply severe fading conditions. Finally, simulation results of the proposed statistical model are compared to measured data demonstrating reasonable agreement.

Rain attenuation is one of the most crucial factors to be considered in the link budget estimation for microwave satellite communication systems, operating at frequencies above 10 GHz. This paper presents a mathematical model for converting terrestrial rain attenuation data to be used for satellite applications at Ku-band. In the proposed technique, the ITU-R P 618-9, together with a combination of ITU-R P 530-12 and the revised Moupfouma model have been adopted for satellite and terrestrial rain attenuation predictions, respectively. The model has been used for transforming the measured rain attenuation data of some DIGI MINI-LINKS operating at 15 GHz in Malaysia, to be used for MEASAT 2 applications. It was found that the model predictions are fairly reasonable when compared with direct beacon measurements in Malaysia and similar tropical locations. The model will provide a relatively accurate method for transforming the measured terrestrial rain attenuation to be used for satellite applications; and therefore substantially reduce the cost of implementing Earth-satellite links in some tropical regions that have sufficient rain attenuation data for the terrestrial links.

In this paper, a wide-slot triple band antenna fed by a coplanar waveguide (CPW) for WLAN/WiMAX applications is proposed. The antenna mainly comprises a ground with a wide square slot in the center, a rectangular feeding strip and two pairs of planar inverted L strips (PIL) connecting with the slotted ground. By introducing the two pairs of PIL's, three resonant frequencies, 2.4/5.5 GHz for WLAN, and 3.5 GHz for WiMAX, are excited. Prototypes of the antenna are fabricated and tested. The simulated and measured results show that the proposed antenna has three good impedance bandwidths (S11 better than -10 dB) of 300 MHz (about 12.6% centered at 2.39 GHz), 280 MHz (about 8% centered at 3.49 GHz) and 790 MHz (about 14.5% centered at 5.43 GHz), which make it easily cover the required bandwidths for WLAN band (2.4--2.48 GHz, 5.15--5.35 GHz, and 5.725--5.825 GHz) and WiMAX (3.4--3.6 GHz) applications. Moreover, the obtained radiation patterns demonstrate that the proposed antenna has figure-eight patterns in E-plane, and is omni-directional in H-plane. The gains of the antenna at operation bands are stable.